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Raising Boost
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mr. dude  



Joined: 15 Feb 2008
Posts: 111
Location: Michigan

PostPosted: Sat Apr 12, 2008 4:01 am    Post subject: Raising Boost Reply with quote

On a side note to my quest for intercooling knowledge I've been reading up on a number of different ways to raise boost levels as well. I've been kicking around the idea of replacing the 0.8 bar wastegate spring with a 1 bar wastegate spring. Is this a good idea to implement without any other modifications such as an intercooler or boost gauge? If so does anyone have a good source for buying one? Thanks in advance.
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Rasta Monsta  



Joined: 12 Jul 2006
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PostPosted: Sat Apr 12, 2008 4:06 am    Post subject: Reply with quote

.8 is ROW spec. US cars had lower boost from the factory.

I have a 1 BAR spring on my workbench. It used to be in the car. Can you guess why I took it out?
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mr. dude  



Joined: 15 Feb 2008
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Location: Michigan

PostPosted: Sat Apr 12, 2008 4:13 am    Post subject: Reply with quote

lol... So you're not recommending this then I take it. Thanks Rasta.

P.S. Is there a prefered or recommended way to raise boost on these cars?
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flosho  



Joined: 01 Jul 2004
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PostPosted: Sat Apr 12, 2008 4:28 am    Post subject: Reply with quote

Just get a cheap manual boost controller and place it inline between the wastegate and charge pipe.. Its a quick 5 min install and you can up your boost. I ran 9 psi without worrying while being non-intercooled.
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mr. dude  



Joined: 15 Feb 2008
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PostPosted: Sat Apr 12, 2008 4:31 am    Post subject: Reply with quote

Cool... Thanks Flosho.
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Maybe924  



Joined: 14 Aug 2007
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PostPosted: Sat Apr 12, 2008 5:07 am    Post subject: Reply with quote

You'll also need to replace your clock with a VDO boost gauge. Without it you'll have no idea how much boost you're running. I ran 10psi on 93 octane with no problems. The extra boost did finally end the life of an old and tired head gasket but I had no detonation problems or any heat issues.

The good news is that if you plan to add an intercooler you'll need to first add the VDO boost gauge and the manual boost controller. So this is a good step in the right direction.

Be warned though do not turn your boost higher than 10psi and do not run on low octane gas. But do enjoy the extra power that will be very obvious.
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Khal  



Joined: 26 Sep 2003
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PostPosted: Sat Apr 12, 2008 5:49 am    Post subject: Reply with quote

Seems to be a bit of confusion surrounding this subject, and for the record, I have no direct practical experience myself (i.e. I've never actually done it, unlike Maybe924 and some others). But I'll put forward my thoughts for consideration:

The U.S. spec. cars had lower boost levels than the 'Euro' spec. cars and, at least in the Series II cars, the U.S. spec. cars had lower compression by way of different pistons. Other than that, to the best of my knowledge, the engines are all but identical. There are other minor differences (at least, what I consider minor with respect to safe boost levels, with my admittedly limited knowledge/experience).

This alone would lead me to believe that you could 'safely' run the U.S. engines up to 'Euro'-equivalent boost levels. I put 'safely' in quotation marks because at the very least, it depends on the condition of your engine and its ancilliaries. A freshly and correctly rebuilt/run-in engine is obviously going to cope better (even at the stock boost levels) than an engine that is ready to let go. So if your engine is a bit tired, I am by no means suggesting that you should just go ahead and boost it up the wazoo...

Over and above 'Euro' boost levels, it seems that many who have been-there-and-done-that strongly advocate intercooling. I personally think intercooling is a good idea no matter what boost you're running and I can't for the life of me comprehend why Porsche never did this straight from the factory on the 924 Turbo... It's obvious the 924 Turbo doesn't need an intercooler, 'cause they all run reasonably well without them when treated properly... but it sure as Hell can't hurt!

And ditto on the boost gauge, of course. You're gonna want one of them if you start screwing around with the boost levels.

Good luck anyway. Let us know if you have some success! (or teach us with your failures )
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jazz guy  



Joined: 26 Nov 2002
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PostPosted: Sat Apr 12, 2008 10:33 am    Post subject: Reply with quote

I have a variable boost controller, and have run 11-12 pounds of boost for many years without an intercooler. I haven't encountered any detonation problems at those levels with good gas. Obviously, the addition of an intercooler would be the best solution, but if your car is in a good state of tune (good compression, a/f set correctly, vacuum leaks fixed, etc.) , it shouldn't be a problem to moderately raise boost.

I do feel that the 1 bar spring is too high to use without an intercooler. I haven't been able to run boost at that level without detonation problems, unless I have added some good octane booster. And on hot days, even octane booster didn't get the job done.

Cheers, Brian
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Rasta Monsta  



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PostPosted: Sat Apr 12, 2008 10:51 am    Post subject: Reply with quote

So, now that you've read all the opinions, wanna buy a 1.0 BAR spring?


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Maybe924  



Joined: 14 Aug 2007
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PostPosted: Sat Apr 12, 2008 1:06 pm    Post subject: Reply with quote

Khal wrote:
I can't for the life of me comprehend why Porsche never did this straight from the factory on the 924 Turbo...


I speculate it was because it would have out performed the 911SC, that certainly wouldn't have gone over too well with the rear-engine die-hards.
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mr. dude  



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PostPosted: Sun Apr 13, 2008 1:58 am    Post subject: Reply with quote

Thanks guys for all of the valuable info. If I do decide to eventually add an intercooler and raise boost I have a number of options now to choose from.

Rasta, hahaha... thanks for the offer but I will have to pass on the 1bar spring now.
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ideola  



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PostPosted: Sun Apr 13, 2008 2:09 am    Post subject: Reply with quote

Khal wrote:
I can't for the life of me comprehend why Porsche never did this straight from the factory on the 924 Turbo...

I suspect cost was also a consideration, given that the 931 was at the bottom of the range.

mr. dude wrote:
I've been kicking around the idea of replacing the 0.8 bar wastegate spring with a 1 bar wastegate spring.

I've been contemplating this for some time as well, particularly as it relates to the UWB project. I expect my setup to require somewhere in the range of 15-17 psi of boost, possible more. My question is whether I should just leave the stock spring in, and control everything with a boost controller, or if there is some better combination of wastegate spring + boost controller that would be better suited to my purposes. I've read a number of the posts on boost controllers and wastegate modification, but I'm still a bit murky on what the ideal combination might be, given a specific BHP target / boost target.
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Eturbo924  



Joined: 09 Nov 2002
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PostPosted: Sun Apr 13, 2008 3:31 am    Post subject: Reply with quote

Question
How much is a moderately priced boost controller?

Also on the 931 and the 951.
Yes they were both held back a bit in order to not completely embarrass the much more expensive 928 and 911s!

If you look at the early test articles with the test mules (931s) from the factory. They were running 0-60 in the high six second range! Then when they came out in production they were more like mid 7s and gasp... in USA trim 9.3 sec! UG.

Anyway have been thinking of 931 for some time and would like to know what kind of boost controller is recomended and what the cost is.
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bass gt  



Joined: 02 Dec 2004
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PostPosted: Sun Apr 13, 2008 3:50 am    Post subject: Reply with quote

Dan,

Your best option is to leave the stock WG spring in place, and fit a DECENT boost controller. Forget spring valves ect. I recommend the Turbosmart EBoost unit. Controls your WG by feeding air into both sides, and controlling the WG accordingly. It is very good, accurate and adjustable. has 6 boost settings, plus lots of other features.
I just don't believe that a spring loaded ball bearing offers enough control over theboost signal, especially when you are looking at such a large increase. If you go to the Turbosmart site, you can download the manual. very impressive piece of kit.
Remember, if you fit a 1 bar spring, that is the LOWEST boost you can run. Use the stock spring, and a decent controller, and the choice is yours.
I know people here may baulk at the cost, but what price a blown motor? You get nothing for nothing in this world

Steve
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Maybe924  



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PostPosted: Sun Apr 13, 2008 5:16 am    Post subject: Reply with quote

Eric,
That 9.3sec 0-60 for that particular test was way off. Its possible that it was a very hot day, or as I suspect something was wrong with the car. That one test has been the bane of the US spec 931 for a long time. The reality is however that even running US spec boost the 931 will easily run high 7s. If you look at other tests of the US Spec cars they'll show you 7.7 sec 0-60 times. There was definitely something wrong with either the car or the driver or both.
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